Conventional corrugators produce single-faced, double-backed and multiple-wall corrugated boards by bonding papers together. Typically, an adhesive is applied to the surfaces of crests of the corrugated portion of the papers. In particular, a starch slurry is prepared as one of ordinary skill in the art will readily recognize using mainly powdered starch and water. Borax and caustic soda may also be added during the preparation of the starch slurry. The prepared starch slurry is often pumped into a reservoir or a pan and applied to flute tips (i.e., crests) of a web of fluting paper by an application roll. A turning doctor roll regulates the thickness of the starch slurry on the application roll to apply to the web of fluting paper, which is typically heated by a corrugating roll. A web of liner paper engages the web of fluting paper at the flute tips such that the starch slurry is absorbed into the web of liner paper as the fluting paper and the liner paper are firmly pressed together. The starch slurry is gelled by the application of heat from the corrugating roll and secures the flute tips onto the liner paper. In particular, during the cooking process, the granules of the powdered starch absorb water, burst, gelatinize and form a glue. The moisture in the glue then evaporates or is absorbed into the liner paper and the glue bonds the liner paper and the flute tips of the fluting paper together.
As one of ordinary skill in the art will readily recognize, the amount of the adhesive required to bond the liner paper with the flute tips of a fluting paper may vary based on the speed of the corrugating process. In particular, more adhesive is required in a corrugating process that operates at a lower speed. However, if the process is operating at a rate that is too slow, virtually all of the water from the starch slurry is absorbed after the slurry is applied to the flute tips and prior to the slurry becoming an adhesive. As a result, no bonds are formed between the liner paper and the flute tips of the fluting paper. Accordingly, more starch slurry is required in the process to simply serve as a carrier of water in order to ensure sufficient amount of water remains in the slurry to form the adhesive.
Further, the inventor has found that as the starch slurry is applied to a dry flute tip provided on a heated, fluted roller, the water of the slurry may be carried through the flute by capillary action at an undesirably fast pace and the starch may effectively dry on the flute. Typically, water from the starch slurry is absorbed into the fluting paper after the slurry is applied and before the slurry becomes an adhesive. Such a phenomenon has at least two negative implications. The first is that the percentage of unusable starch may be sufficient to degrade the effective adhesive quality of the slurry, thereby producing less than optimum product. The second is that manufacturers are required to compensate for this contingency by applying more starch to the flutes than would ordinarily be received to produce an effective bond, thereby reducing efficiency and increasing cost. It would therefore be advantageous to apply the starch slurry to the flute tips of the corrugated paper in a more efficient and effective manner. In particular, it would be advantageous to reduce the amount of starch slurry applied to the flute crests and accordingly reduce the cost of producing corrugated boards, while at the same time maintaining or improving bond quality.